Everyone has internal dialog. Some people just audibly verbalize it.
Some people mistakenly call it 'god'.
Some people mistakenly call it 'god'.
You'd believe if you just opened your heart" is a terrible argument for religion. It's basically saying, "If you bias yourself enough, you can convince yourself that this is true." If religion were true, people wouldn't need faith to believe it -- it would be supported by good evidence.